The present invention relates to a double sealed valve comprising: a valve seat in a communicating passage formed between an upper passage and a lower passage;
a first vertical valve stem and a second vertical valve stem, which is hollow, slidably surrounding that first valve stem;
said first stem having a first valve plug;
said second stem having a second valve plug and a valve drive mechanism connected to said stems.
Such a valve is known by EP 0 819 876 A3. These valves are mainly used in plants producing food stuff.
For cleaning and maintenance of the valve, the upper and lower passage can easily be separated by opening a clamp ring joining and fixing two adjacent flanges of the upper and lower passage. The connecting flanges are both bearing a recess, wherein the valve seat is held. The remaining upper and lower flanges of the upper and lower passage are designed in the same manner and an upper and lower sealing arrangement are directly clamped to the upper and lower flange by said clamp rings.
Further there is provided a valve drive mechanism, to actuate the stems. This valve drive mechanism is to be fixed also to the upper or lower passage which altogether form the double sealed valve. The valve drive mechanism is held by a yoke, which is bearing also a flange, being clamped by the clamp ring to the flange of the upper passage.
The cleaning fluid is fed through a supply opening to two passages namely to a first passage being an annular space between the first and second vertical valve stem and to a second passage being a axial bore in the first valve stem. The flow of the cleaning fluid leaving the outlet opening of the first passage into the annular space between the first and second valve plug is directed in axial direction whereas the flow of cleaning fluid of the second passage is directed partly horizontal when leaving its outlet opening. Both flows are interfering which each other giving a poor cleaning effect in the annular space between the valve plugs. The provision of two passages for feeding the cleaning fluid makes the design of the valve more complicated and expensive.
In EP 0 760 447 A 1 there is disclosed an automated pipe connection with caps for preventing intrusion of sundry bacteria into couplers for performing washing and/or sterilization operation. Inside the upper valve stem the washing water is fed via a hose and sprayed out through spraying means for example making use of small holes bored in tangential directions to spray each fluid in the form of a swirl to wash the seal of the upper and lower valve elements in the cleaning chamber. The only passage for cleaning fluid is shown as an axial bore of the upper valve stem. There are no two telescopically arranged valve stems but the valve stems are actuated from opposite sides. Therefore there is also no passage between two telescopically arranged valve stems. It is not disclosed how the cleaning fluid is fed to the bore in the upper valve stem.
The U.S. Pat. No. 4,605,035 describes a double seat valve including a valve housing and two closure members movable in the housing coaxially and relative to each other between an open and closed position. The top and/or bottom opening are sealed by a sealing arrangement, formed as a sleeve with an annular passage for cleaning fluid, whereby the annular passage is provided with a supply fitting having a supply opening. The disadvantage of this arrangement is, that the cleaning fluid flows from this supply opening on a direct path to a discharge opening giving insufficient cleaning effect at dead ends.
In food-technology or other sanetary aseptic-technologies, it is of great importance, that all the parts of the valve may be cleaned in place (CIP). But in certain intervals the valves have to be taken apart to allow thorough cleaning. All ports for cleaning fluid and passages for the cleaning fluid within the valve make the valve more complicated and make it more difficult to take it apart.
There is the need to enlarge the cleaning intervals by improving the cleaning efficiency of the fed cleaning fluid. But increasing the flow of cleaning fluid causes undesirable additional costs. There is also the need for cost reduction when using such equipment. These objects are in part contradictionary. Anyhow it is an object of the invention to achieve an external CIP-(cleaning in place)-system that needs as little as possible of CIP-liquid and time for sufficient cleaning of the leakage chamber and stems.
An further object of the invention therefore is to allow easier mounting and demounting of the valve to reduce the shut down time of the plant.
To solve this object a double sealed valve being subject of the invention having between the first vertical valve stem and the second valve stem a passage for cleaning fluid is defined, being sealed towards the valve drive mechanism and having an outlet opening towards an annular space between the first and second valve plug is proposed, wherein the outlet opening of the passage is formed by a spray disc having jet openings with an outletdirection which is horizontal and inclined with respect to a radial direction of the valve stem causing a helical flow in the annular space for cleaning the annular space. Surprisingly it has been found that the cleaning efficiency is better when the jet of the cleaning fluid hits substantially horizontal the surface under a flat angle causing a helical flow than hitting it rectangular and flowing from this point radially. That means the cleaning fluid is directed by a spirally arranged groove to form a jet which hits the wall with a velocity vector component in circumferential direction and flowing then influenced by gravity and pressure difference in helical like manner along the wall of the annular space.
In a preferred embodiment, the spray disc is mounted by means of a snap-lock to the hollow second valve stem being slidingly protruded by the first valve stem. This allows to mount the spray disc easily thereby reducing shut down time for cleaning. The disc can be easily pressed into the annular groove formed into second valve plug.
In another preferred embodiment the snap lock fits in a groove having the same dimensions as for receiving a sealing ring. In older valves without CIP cleaning in this groove a sealing ring is mounted. The valve can easily be upgraded by providing CIP cleaning facilities because the snap lock fits in a groove having the same dimensions as for receiving a sealing ring.
The costs are advantageously reduced if the spray disc is formed from plastic, preferably by injection moulding. In the spray disc nozzles may be formed with spiral like groves causing a helical flow cleaning the surfaces in the leakage chamber by means of the formed jets.
In a preferred embodiment the second vertical hollow valve stem is divided in two parts connected by a coupling, bearing a port for a cleaning fluid. The valve drive mechanism can be easily disassembled, by disconnecting the valve stems. At the same time also the feed for the CIP-liquid is disconnected.
In another preferred embodiment the coupling consists of axially split bridging parts which protrudes into an undercut or groove of the hollow valve stem, and wherein the bridging part is being held by an unsplit sleeve. By this design, the valve stems can easily be connected without needing special tools.
In an advantageous embodiment the port for cleaning fluid serves two functions. It not only feeds the CIP-liquid, but it also locks the parts of the coupling in that the sleeve and the split bridging part are locked by a port for cleaning fluid protruding the sleeve and one part of the split bridging parts.
Any leakage of the coupling can be prevented, if the parts of the hollow stem are additionally bridged by a sealing pipe member.
The object of the invention is also solved by a valve according to the subject of the invention having the top and/or bottom opening which are sealed by a sealing arrangement, formed as a sleeve with an annular passage for cleaning fluid wherein the annualar passage is provided with a supply fitting having a supply opening whereby the supply opening is formed as a cross bore in a blind ending bore of the fitting, protruding into the annular passage whereby the cross bore has an axis being arranged substantially horizontal. This design causes a helical flow of CIP-fluid in the annular passage along the sealing surface preventing thereby impurity parts to be pressed into the sealing gap by the pressurised CIP fluid. The wear of the seals and the sealing surface is advantageously reduced thereby.
The costs are reduced if the annular passage is provided with a outlet fitting having an opening with an area which preferably exceeds the area of the supply opening, and the fitting being formed the same shape as the supply fitting but without the blind end and the cross bore.
The object of the invention is also solved by a valve according to the subject of the invention having top and/or bottom opening sealed by a sealing arrangement, formed as a sleeve with an annular passage for cleaning fluid, wherein the sealing arrangement is mounted between an upper and lower passage connecting flange and a fixing ring, which form together a fixing groove wherein a collar of the upper and lower sealing arrangement is held. This allows easier maintenance of the valve, since all sealings are more easily accessed.
The number of parts are advantageously reduced, in that the upper and lower sealing arrangement are formed identical.